Method of corrugating a heatradiating tube



June 25, 1940. M, UNGER METHOD OF CORRUGATING A HEAT-RADIATING TUBEFiled Sept. 5, 1937 2 Sheets-Sheet 1 Fi m Fig. 9

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METHOD OF CORRUGATING A HEAT-RADIATING TUBE Filed Sept. 5. 1957 '2Sheets-Sheet 2 Inventor": Mangus Un er; b #W a M 9 His Attorneg.

Patented June 25, 1940 PATENT METHOD OF CORRUGATING A HEAT- RADIATINGTUBE Magnus Unger, Pittsfield, Masa, assignor to General ElectricCompany, a corporation of New York Application September 3, 193?, SerialNo. 162,250

2 Claims.

My invention relates to a method of forming metal tubes for heatradiators. The invention provides a tube particularly adapted for use ina heat radiator for cooling the insulating liquid in which electricalapparatus such as transformers are immersed. Heat-radiating tubes ofround cross-section are often used in heat radiators. By corrugating thetube, however, the amount of liquid in the tube is substantially reducedwith little corresponding reduction in the rate at which heat isdissipated. The corrugated tube is therefore substantially as efiicientin dissipating heat as is the round tube and a considerably smallerquantity of expensive insulating liquid is required. The general objectof the invention is to provide an improved method of forming aheat-dissipating metal tube.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawings in which Fig. 1 is asectional view of part of a liquid-immersed transformer provided with aheat radiator including heat-radiating tubes formed in accordance withthe invention; Fig. 2 is an explanatory detail view, partly in section;Figs. 3, 4, 5 and 6 are views indicating steps in the preferred form ofthe process for forming a heat-insulating tube in accordance with theinvention; Figs. 7, 8, 9 and 10 are views indicating steps in a modifiedform of the process; Figs. 11 to 18 inclusive are views indicating stepsin another form of the process; Fig. 19 is a perspective view of aportion of a partly-formed tube and parts of a die used in the process.

Like reference characters indicate similar parts in the differentfigures of the drawings.

The heat-radiating tubes ill, formed in accordance with the invention,are shown in Fig. 1 as being assembled between an upper header l l and alower header l2 to form a radiator for cooling the insulating liquid l3in which a transformer it is immersed. The ends of a round tube arereduced in diameter by any desired method, such as the swaging methoddisclosed in my Patent No. 1,895,947, issuedv January 31. 1933, andassigned to the General Electric Company. The round tube with itsreduced ends is then placed between two die members l5, as indicated inFigs. 3 and 19. The preferred form of die is shown in Figs. 3, 4, 5, 6and 19. The two die members l5 are alike and are approximately as longas the tube ill. The face of each die member is formed with a groove orchannel IS with symmetrical convex sides. The round tube lll with itsreduced ends is placed between the die mem- 55 bers IS with no internalsupport for the tube,

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as indicated in Figs. 3 and 19. The die members are then forced towardeach other as indicated in Fig. 4. Two convex sides of each die memberapply pressure in parallel directions to two spaced longitudinalportions of the tube with which they are in contact. This-presses thetwo sides of the tube next to the die members it toward each other andproduces two sharp, longitudinal convex bends ll along the sides of thetube, the diameter of the tube in the direction of the presto sure beingreduced and its diameter at right angles thereto being increased. Thedie members are now separated and the tube it turned ninety degrees withits sharp bends ii in the bottoms of the grooves l6 of the die members,still in with no internal support for the tube, as shown in Fig. 5. Theincreased diameter of the tube is then reduced until the two diametersare substantially equal by pressing the die members it together, asindicated in Fig. 6. to form two more an longitudinal, sharp convexbends it in the tube it, the longitudinal bends I1 and I8 being ofcourse uniformly spaced and the convex bends being joined by concavetube portions l9 formed by the convex sides of the grooves it of the dieg5 members. The grooves l6 and their convex side faces are preferably sospaced and proportioned that when the die members I5 are pressedtogether, as indicated in Figs. 4 and 6, the convex side faces of thegrooves it will just meet the so outer surfaces of the reduced endportions of the tube ill. The convex side faces of the grooves it thusserve to assure proper alignment of the tube ill along the axis of thedie and consequent symmetrical formation of the tube when the die pgmembers are pressed together.

A modified form of the process of forming the tube It is indicated inFigs. '7. 8, 9 and 10, Where the round tube Ill is first pressed betweentwo die members 20 with their faces having grooves M with plane sidefaces. The die members 20 are then separated, the tube It] turnedthrough ninety degrees and the die members 20 again pressed together togive the tube ill a square cross-section except that the corners areslightly rounded. The M tube If! is next pressed between two die members22 having faces with grooves 23 with convex side faces, as shown in Fig.9. In this step of the process the die members 22 are not pressed quitetogether but only until the two longitudinal, m sharp bends 24 areproduced. The die members 22 are then separated, the tube turned throughninety degrees and the die members 22 again pressed together, as shownin Fig. 10;, to give the tube I9 its final symmetrical configurationwith bers 26, as indicated in Fig. 11, and the die members pressedtoward each other, as indicated in Fig. 12, until the two longitudinalbends 21 are formed in the tube. These longitudinal bends 21, however,are not as sharp as is finally desired. The die members 26 are thenseparated, the tube turned through ninety degrees, as indicated in Fig.13, and the die members 26 again pressed partly together, as indicatedin Fig. 14, until two more longitudinal bends 28 are formed but not withthe finally desired degree of sharpness. The die members are thenseparated, the tube l0 turned through ninety degrees, as indicated inFig. 15, and the die members then pressed together, as shown in Fig. 16,to give the longitudinal bends 28 their finally desired sharpness. Thedie members 26 are then again separated, the tube l0 turned throughninety degrees, as

indicated in Fig. 17, and the die members 26 again pressed together togive the longitudinal bends 2'! their final degree of sharpness as shownin Fig. 18 and the tube l0 its final symmetrical configuration. In thisform of the method, indicated in Figs. 11 to 18 inclusive, thelongitudinal sharp bends in the tube are produced more gradually withless tendency to crack the tube than in the preferred form indicatedin'Figs. 3 and 6 and the greater number of steps involved may be adoptedif found desirable.

The invention provides a very rapid and efflcient but simple method forproducing a corrugated heat-radiating tube by pressing corrugations intothe outer surface of the tube but without the necessity of providing anyinternal support for the inner surface of the tube. The invention hasbeen explained by describing and illustrating a corrugatedheat-radiating tube and steps for producing it but it will .be apparentthat changes may be made without departing from the spirit of theinvention and the scope of the appended claims. 7

What I claim as new and desire to obtain by Letters Patent 01' theUnited States is:

1. The method of corrugating a heat-radiating tube of round crosssection, said method including the steps of applying pressure 'inparallel directions to two spaced longitudinal portions of each of theopposite sides of the tube andwith no internal support-for the innersurface of the tube to collapse the tube and form a first pair ofrelatively sharp convex bends in diametrically opposite portions of thetube between said two sides, rotating said tube through a right angleand then applying pressure to two spaced longitudinal portions of thetube at the two convex bends to collapse the tube and form asecond pairof relatively sharp convex bends in diametrically opposite portions ofthe tube at right angles with respect to said first pair of bends.

2. The method of corrugating a heat-radiating tube of round crosssection, said method including the steps of applying a first pressure inparallel directions to two spaced longitudinal portions of each of theopposite sides of the tube and with no internal support for the innersurface of the tube to collapse the tube and form two longitudinalconcave portions in each of the I opposite sides of said tube andforming a first pair of relatively sharp longitudinal convex bends indiametrically opposite portions of the tube between said two oppositesides, applying a second pressure in parallel directions at right anglesto said first pressure at said concave portions on opposite sides ofsaid first pair of bends to further collapse the tube and form a secondpair of relatively sharp convex bends in diametrically opposite portionsof the tube at right angles with respect to said first pair of convexbends.

MAGNUS UNGER.

